I just put 4 new bulbs in my 3rd brake light yesterday after a couple months of it not working and when I turned my light on to see if they worked, they didn't. I checked everything i could think of checking but the only thing I can think of that would stop them from working is a missing fuse. I popped the cover off my fuse box and the spot where there is suppose to be a 15amp fuse for quad lamps has no fuse and I'm wondering if that is where the fuse for the 3rd brake light is. I've only been able to get a look at a 98 and its fuse box is just slightly different from my 99, it doesn't have a quad lamp fuse slot. So if anyone knows if my guess is correct or not can you please chim in and let me know what you think.

 

Come on guys, anyone have anything to say about this? I now know its not the quad lampfuse because I compared my fuses two and buddies fuse box at work and he doesn't have a quad lamp fuse installed either. So I'm guessing I may need to replace the wires for it.

 

Well... looking at the schematic in the FSM... All of your brake lamps are fed by fuse #5, which is a 20A fuse. It will be in the fuse box that is located under the hood.

If your rear brake lights are working properly, but your 3rd brake light is not, it's likely a wiring problem because a blown fuse would cause all of your brake light to fail.

I would check to see if you are getting power to the 3rd brake light using a volt meter (white/tan wire). If you are getting power, but no light functionality - the problem is likely your ground (black/light green wire)from the 3rd housing.

If you are not getting power - then the problem is on the power feed side. Check to make sure that the connector is properly attached. Check for frayed or cracked wires. If everything looks good there... you would have to work backwards to find the source of the break. But most of the connections up stream are in places that are not likely to be broken.

I would suspect that perhaps the ground wire got disconnected and forgoten - especially if you still have rear brake light functionality.

Good luck,
Cartman

 

I sent you a pm about this but i used to own your truck. when i had it, it had a canopy. the owner before me bypassed the 3rd brake light becuase the canopy had one. once i took the canopy off i never got around to fix it. Also the owner before me bypassedthe fog lights some how. it tried to do the high beam mod but found just like you that the relay was gone. Maybe any of this can help